This invention relates to a composite tube for a gun barrel and more particularly to a composite tube including carbon fibers and a resin matrix material, with breech and muzzle pieces attached to the gun barrel by an adhesive or threads and enclosing the resin matrix material, so that vibrations in the barrel are reflected into the resin matrix material by the breech and muzzle pieces.
Composite gun barrels are desirable because they permit the construction of lightweight firearms. A composite barrel such as one constructed from a tube made of carbon fiber and epoxy resin materials, however, typically lacks sufficient stiffness to maintain its integrity for accurate reproducible firing. Even when the composite barrel includes an inner tubular liner, a firearm having such a composite barrel tends to be less accurate than a firearm having a conventional barrel.
A composite tube and method of manufacture for a gun barrel is disclosed in U.S. Pat. No. 5,600,912, herein incorporated by reference, and invented by the same inventor. While the composite tube there disclosed has certain advantages over the prior art, the inventor has found that the improvements disclosed and claimed herein add greatly to the accuracy of fire of the gun barrel.
More particularly, the receiver of a firearm in combination with a steel barrel acts like a bell. Since the steel barrel is of one homogeneous material, when a cartridge is fired, the entire system vibrates at a particular frequency. Such vibrations are generally detrimental to the performance of the barrel.
Such vibrations travel down the length of the barrel as soon as the trigger is released and the cocking piece strikes the primer of the cartridge, due to metal-to-metal contact in an all-metal structure. Upon ignition, these vibrations or harmonics increase. As the vibrations travel down the barrel, they cause the barrel to vibrate at a group of frequencies. In the past, part of the art of gunsmithing was to achieve appropriate barrel length to be consistent with the wavelength of these frequencies to minimize barrel vibration.
Barrel vibration causes a bullet to be deflected from the target line, resulting in inaccuracy of fire.
U.S. Pat. No. 5,600,912 disclosed a barrel which helps to eliminate these harmonic vibrations by absorbing the vibrations into a carbon fiber material oriented longitudinally along the barrel. However, the invention disclosed there does not fully eliminate harmonics which reach the muzzle and breech pieces, because the muzzle and breech pieces are not tightly integrated with the carbon fiber material. Also, the carbon fiber material in the ""912 patent is not compressed sufficiently to produce optimum fiber density in the resin matrix material.
There is a need for a composite tube for a gun barrel which overcomes the above-discussed deficiencies.
A composite tube for a gun barrel consists of: an inner tubular metal liner defining a longitudinal bore axis; a resin matrix material surrounding the liner, the resin matrix material containing a plurality of elongate carbon fibers, the carbon fibers being aligned parallel with the longitudinal bore axis of the liner and under compression along the longitudinal bore axis; a muzzle piece attached to the muzzle end of the barrel by adhesive and/or threads; and a breech piece attached to the breech end of the barrel by adhesive and/or threads, so that any vibrations transmitted along the longitudinal bore axis of the liner are absorbed by the resin matrix material and so that any vibrations reaching the muzzle piece and breech piece are reflected back into the resin matrix material and thus absorbed.
A method of manufacturing the composite tube for a gun barrel consists of the steps of:
a) grinding the metal liner down from its original thickness to a greatly reduced thickness;
b) applying the resin matrix material in layers about the metal liner by wrapping a carbon fiber mat with embedded resin about the metal liner under extreme pressure, until a suitable thickness of resin matrix material has been applied to the metal liner;
c) compressing the wrapped resin matrix material;
d) heating the wrapped resin matrix material and enclosed metal liner while maintaining compression on the resin matrix material to cure the resin matrix material;
e) lathing and sanding the cured resin matrix material to the proper diameter for a gun barrel; and
f) attaching the muzzle piece and breech piece to the gun barrel.
A principal object and advantage of the present invention is that the breech and muzzle pieces transmit any vibrations from the barrel and receiver back into the resin matrix material, where they are absorbed.
A second principal object and advantage of the present invention is that the method of manufacture rolls the resin matrix material onto the metal liner under extreme pressure, and the resin matrix material is held under strong compression during the manufacture and cure cycles, resulting in greatly increased carbon fiber density in the cured material, with a greatly increased ability to absorb vibrations.